1. Field of the Invention
This invention relates to methods for preparing a protein-enriched pectin composition and the use of this material in making a dietary supplement rich in protein concentration.
2. Related Art
Pectins are a group of high-molecular-weight heterogeneous polysaccharides which serve as fundamental structural components of plant cell walls in fruits and vegetables, particularly limes, lemons, grapefruit, and oranges. Pectin is composed of D-anhydrogalacturonic acid units linked through .alpha.(1.fwdarw.4)-glycosidic bonds forming a polygalacturonic acid with some of the carboxyl groups esterified with methanol. Since pectin is not susceptible to hydrolysis by the alimentary tract enzymes of humans, it is classified as a dietary fiber.
Pectin products are normally manufactured by aqueous extraction of appropriate edible plant material such as those enumerated above. Food grade pectin consists of partially methylated polygalacturonic acid units and is normally classified according to its degree of esterification or methoxy content.
In high ester- or high methoxyl (HM)-pectin, a relatively high portion of the carboxyl groups occur as methyl ester and the remaining carboxylic acid groups are in the form of the free acid or as its ammonium, potassium, calcium, or sodium salt; its useful properties may vary with the degree of esterification and with the degree of polymerization. Pectin in which less than 50% of the available carboxyl acid groups occur as the methyl ester is normally referred to as low methoxyl (LM)-pectin. In general, LM pectin is obtained from HM pectin by a treatment such as mild acid or alkaline conditions. Amidated pectin is obtained from HM pectin when ammonia is used in the alkaline deesterification process. In this type of pectin, some of the remaining carboxylic acid groups have been transformed into the acid amide. The useful properties of amidated pectin may vary with the properties of methoxyl and amide substitutions and with the degree of polymerization. Commercial pectin is normally blended with sugars for standardization purposes, and some types may contain suitable food-grade buffer salts required for pH control and desirable setting characteristics.
Since it is a constituent of all plants, pectin has long been part of the human diet. Pectin has been evaluated and cleared toxicologically by the Joint FAO/WHO Expert Committee on Food Additives. Consequently, it was deemed unnecessary to establish an acceptable daily intake. National and international food regulations recognize that pectin is a valuable food gelling agent and harmless food additive. Pectin is included in the list of permitted additives in standardized foods when a technological need can be proven.
U.S. Pat. No. 4,497,838 describes the preparation of various orange products from orange peels. The preparation involves extraction of orange peels with a non-aqueous water-miscible solvent. The solvent-extracted peel is dried to produce a product high in cellulose and pectin. The dried peel product is then ground by suitable means such as a hammer mill to a size appropriate for its intended use.
Pectin has been shown to be an effective hypocholesterolemic agent with minimal side effects (Reiser, Food Technol., 41-91, 1987). It has also been found that grapefruit pectin inhibits hypocholesterolemia and atherosclerosis in miniature swine (Baekey, et al., Clin. Cardiology, 11:595-600, 1988). Furthermore, grapefruit pectin has proven to lower plasma cholesterol levels in human volunteers who were hypercholesterolemic, and to improve the ratio of low density lipoprotein cholesterol (LDLC) to high density lipoprotein cholesterol (HDLC) (Cerda, Clin. Cardiology, 11:589-594, 1988).
Based on epidemiological and experimental studies, it is clear that the causative factor for coronary heart disease is associated with high plasma lipid and lipoprotein levels. Further, evidence is abundant that lowering lipid levels by diet and/or drugs reduces the risk of coronary heart disease.
In view of the above, pectin-rich food compositions would be useful adjuvants in a fat-restricted diet of a hypercholesterolemic patient, or in a diet aimed at the primary prevention of atherosclerosis in healthy individuals. Thus, simple methods which allow the manufacture of pectin-enriched food compositions are needed to provide the general public with dietary forms of pectin. The present invention provides a preparation method which achieves this goal.